Our objective is to study the structure-activity relationship of corticotropins (ACTHs), lipotropins (LPHs), endorphins (EPs), melanotropins (MSHs) and related peptides. It is planned to isolate ACTH, Beta-LPH, Beta-EP and related peptides from elephant pituitary glands and to determine their amino acid sequences. Once the structure is known elephant ACTH, Beta-EP and related peptides will be synthesized by the solid-phase method. It is also planned to synthesize dogfish and amphibian ACTHs. When the synthetic peptides become available, their biological properties are investigated. Alphah-ACTH-(7-38) [corticotropin-inhibiting peptide (CIP)], the naturally occurring inhibitor to ACTH, is a weak antagonist. It is hope to synthesize analogs of CIP with higher inhibitory activity. Similarly, it is planned to synthesize analogs of Betah-EP-(1-27), [Beta-EP inhibiting peptide (BetaEIP)], the naturally occurring inhibitor to Beta-EP-induced analgesia, with higher inhibitory activity. For the development of sensitive and specific radioimmunoassays (RIAs) for rat and human Gamma-LPH, it is necessary to synthesize these two Gamma-LPHs by the solid-phase method. ACTH and related peptides are known to exhibit no three dimentional structures in water. It is planned to investigate the presence of a tertiary structure in aqueous solutions of human ACTH, Beta-MSH and Alpha-MSH by difference absorption spectroscopy of enzymic digests of the hormones.